1. Technical Field of the Invention
This invention relates to a method and system for reducing emissions and improving performance of an internal combustion engine by providing oxygen-enriched air and nitrogen-enriched air to a combustion chamber.
2. Description of Related Art
The purpose of an internal combustion engine is to convert the chemical energy of fuel into the mechanical energy of motion using a process of combustion. As is known, internal combustion engines are used extensively in a variety of machines including mobile vehicles, or for other purposes, such as power generation. However, internal combustion engines produce emissions from the combustion process which include a number of pollutants whose presence are undesirable in the environment. As a result, numerous regulations have been implemented by various government bodies requiring reductions in these pollutants. The primary pollutants produced by internal combustion engines during the combustion process include oxides of nitrogen (NOx), carbon monoxide (CO), particulate matter (PM), and hydrocarbons (HC). Nitrogen oxides (NOx), such as nitric oxide and nitrogen dioxide, are formed during the combustion process when air combines with oxygen under the high temperature conditions of the engine's combustion chamber. Nitrogen oxides contribute to the formation of ozone, smog, and acid-rain. Carbon monoxide is formed during the combustion process from the incomplete combustion of the air-fuel mixture. Carbon monoxide is a colorless, odorless, and toxic gas, and is one of the most dangerous of the combustion process pollutants. Particulate matter is also formed during incomplete combustion and consists of a mixture of solid and liquid matter whose main constituent is carbon. Particulate matter is a major source of visible urban air pollution such as soot and haze. Hydrocarbons are formed from the combustible fuel and lubrication oils and additives used within the engine. Both particulate matter and hydrocarbons are suspected carcinogens. In comparison to gasoline engines, diesel engines have particularly high concentrations of nitrogen oxides and particulate matter contained in their emissions.
It has been known in the past that the introduction of oxygen-enriched air into the combustion chamber during the combustion process allows for more complete combustion and results in a reduction in the formation of particulate matter, carbon monoxide, and hydrocarbons. An increase in fuel efficiency, as well as engine power, can also be achieved through oxygen-enrichment. However, oxygen-enrichment of the combustion process results in an undesirable change in NOx production, as well as an increase in combustion temperatures, which can cause engine overheating. An example of an oxygen-enrichment of intake air is described in U.S. Pat. No. 5,636,619. The method described in U.S. Pat. No. 5,636,619 requires the use of a suitable NOx after-treatment device in the exhaust stream to attempt to reduce the higher level of NOx generated by the oxygen-enrichment. However, U.S. Pat. No. 5,636,619 does not offer a solution to the problem of engine overheating caused by oxygen-enrichment of intake air.
The introduction of nitrogen-enriched air into the exhaust stream of an internal combustion engine has also been known in the past to reduce NOx present in the exhaust gases. U.S. Pat. No. 5,640,845 describes a NOx reduction method which includes the injection of atomic nitrogen into the exhaust gases of an internal combustion engine. However, U.S. Pat. No. 5,640,845 also does not offer a solution to the problem of engine overheating caused by oxygen-enrichment of intake air.
The present invention provides for a reduction in emission pollutants, as well as increased fuel efficiency and engine power, while reducing or eliminating the disadvantages of prior methods. The introduction of nitrogen-enriched air into the combustion chamber after the start of combustion provides for a reduction in the formation of NOx, while reducing or eliminating the problem of engine overheating caused by oxygen-enrichment of intake air.